Frame for dynamo-electric machines.



N0. 7I0,425. Patented Oct. 7, I902.

A. J. CHUBCHWARD.

FRAME FDR DYNAMO ELECTRIC MACHINES.

(Application filed Sept. 12, 1896.)

(No Model.) A

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ALEXANDER J. CHUROIIYVARD, OF BROOKLYN, NEW YORK.

FRAME FOR DYNAMO-ELECTRIC MACHINES.

SPECIFICATION forming part of Letters Patent N 0. 710,425, dated October '7, 1 902.

Application filed $eptemher 12, 1896. Serial No. 605,5 93. (No model.)

To all whom it may concern:

Be it known that I, ALEXANDER J. CHURCH- WARD, a citizen of the United States, and a resident of Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in Frames for Dynamo-Electric Machines, of which the following is a specification.

This invention relates to an improvement in dynamo-- electric machines, and particularly to the frames of such machines,and specifically to the pole-pieces which constitute portions of the frame.

Heretofore it has been usually considered necessary to make the free ends or faces of the polesthe pole pieces or shoes-for generators and motors of as great area as possible, extending them far beyond the magnetcores. So, also, a metal of low permeability, such as cast-iron, has been considered undesirable and unfit for magnetic cores or polepieces for the field-magnets of dynamo-electric machines; but in a machine designed after my invention these features are most desirable. In those electrical machines using toothed armature-cores the air-gap has got to be reduced as much as possible when the cores and pole-pieces of the field-magnets are cast-steel, wrought-iron, or laminated iron, and if no pole-shoes are used the air-gap has to be so narrow that the pole-tips become heated. If pole-pieces of cast-steehwroughtiron, or laminated iron are used, the demagnetization thereof by the counter magnetism of the armature necessitates the employment of additional copper in the field-coils to neutralize this tendency to demagnetization. Then with this additional amount of copper it is necessary to make the air-gap quite large to prevent the pole-pieces from becoming heated and demagnetized.

The object of my invention is to overcome these defects and objections and to produce a frame for dynamo-electric machines, both generators and motors, of increased efficiency and at greatly reduced expense.

To this end my invention consists in aframe for dynamoelectric machines made wholly from metal of low permeability, the cores and pole-pieces being integral parts of the frame.

It also consists of a field magnet having a pole-piece of a size and shape such that it will become magnetically saturated sooner than does the core 'of the magnet.

The invention further consists in the construction, combination, and arrangement of parts, as hereinafter fully described, and set forth in the claims.

In the accompanying drawings, which form a part of this specification, Figure 1 is an end representation, partly in section, of the field portions of a dynamo-electric machine embodying my invention. Fig.2 is a like view of an ordinary form of dynamo-electric machine. Fig. 3 is a detail showing the relation of the improved pole-piece to a slotted armature. Fig. at is a face view of the pole-piece. Figs. 5 and 6 are transverse sections on lines 5 5 and 6 6, respectively, of Fig. at.

In describing the invention the term frame is used to embrace that much of a dynamo-electric machine which consists of the containing-frame A, the field-magnet cores B, and the pole-pieces O. The fieldma-gnet coils are represented at D, and the armature appears in outline at E.

In my improved machine the three elements of the frame just mentioned are castintegral with one another and from cast-iron. This makes the cheapest sort of frame that can be produced, and when formed as herein set forth it makes possible the construction of a dynamo-electric machine of higher efficiency than those heretofore in use. Other metal of low permeability besides cast-iron maybe used; but, all things considered, cast-iron is found to be the best. The pole-pieces are preferably made to conform to the contour of the armature, as indicated, and are reduced, as shown, to an area in cross-section less than that of the magnet-cores. This may be done in several ways, as by chamfering the corners and preferably by chamfering them only partially across,as in Figs. 4 and (3. This reduction in the extent of the pole-pieces provides for a more complete passage of the lines of force into the armature. It also provides a greater space between adjacent pole-pieces. This space I have found to be' best proportioned when equal to the width of the polepieces, thereby exposing one-half the surface of the armature. This arrangement greatly increases the ratio between the distance from the pole-pieces to the armature and the dis- IOO tance between the pole-pieces, thereby insuring a complete collection of the lines of force by the armature. In the old form of machine, as indicated in Fig. 2, the pole-pieces approach nearer to each other and allow a flow of magnetism from one to the other, which flow is augmented by the armature reaction. By my construction this is impossible. By the decreased area of the pole-pieces with respect to that of the cross-section of the cores and in metal of low permeability any tendency of the armature to demagnetize the the magnetism from the cores to flow directly to said tips,as indicated bythe arrows in Fig 3. If the pole-pieces were chamfered off abruptly-as, for example, if they were throughout of the cross-section shown in Fig. 5-the armature-coils to be commutated would enter abrutly into the field, thereby causing imperfect commutation and sparking. To avoid this, I so proportion and shape the pole-pieces that the coils to be commutated will enter gradually into the field, thereby affording perfeet and sparkless commutation. To this end I make the pole-pieces to vary in lateral extent, so that some portion of the pole-piece shall project to greater width than the remaining portion in order to afford a graduallyentrant field. A suitable shape is that shown in Fig. 4, where on the line 6 6 the pole-piece is of full Width, as shown in Fig. 6, and to either side of this line it gradually is reduced in width until the chamfered section shown in Fig. 5 is reached.

\Vhat I claim as my invention is 1. In a dynamo-electric machine, the combination with a field-magnet having unlaminated cores of metal of low permeability, the pole-pieces thereof having less area in crosssection than the cores of the magnetizingwindings, whereby the pole-pieces become magnetically saturated in advance of the cores, substantially as and for the purpose setforth.

2. In a dynamo-electric machine, the combination with a field-magnet having unlaminated cores of metal of low permeability, the magnet-cores and the pole-pieces being integral parts of the frame, the pole-pieces being of less cross-sectional area adjacent to the armature, than the cores of the magnetizingwindings, whereby the pole-pieces become magnetically saturated in advance of the said cores, substantially as described.

3. In a dynamo-electric machine, the combination with an armature, of a field-magnet frame therefor, and cores of metal of low permeability provided for said field magnet frame, the pole-pieces of said cores being of less area in cross section than the cores, whereby the pole-pieces become magnetically saturated in advance of the cores, the width of the pole-pieces opposed to the armature decreasing toward the extremities, whereby a grad uallyentrant field for the said armature is produced, substantially as described.

4:. In a dynamo-electric machine, the combination with an armature, of a field-magnet frame therefor, and cores of metal of low permeability provided for said field magnet frame, the pole-pieces of said cores being of less area in cross-section than the cores, whereby the pole-pieces become magnetically saturated in advance of the cores, the width of the pole-pieces opposed to the armature varying in lateral extent longitudinally of the said armature, substantially as described.

Signed at New York, in the county of New York and State of New York, this 10th day of September, A. D. 1896.

ALEXANDER J. CIIURCHWARD. Witnesses:

WM. H. CAPEL, D. H. DECKER. 

